Wireless communications, specifically push-to-talk (PTT) communications, have been and continue to be a critical tool used by public safety officers to coordinate and communicate. As wireless communications technology has advanced (e.g., digital radio systems, broadband communications, voice over Internet Protocol (VoIP), etc.), the overall public safety communications system environment has become diversified, prompting the development and adoption of standardized network-to-network interfaces (NNIs).
A NNI defines the basic messaging and procedures for establishing and handling communications between disparate or separate communications systems. This allows a public safety officer to continue communicating with other members of the team while roaming or to attach their PTT communications device, called a subscriber unit, to a foreign communications system when on assignment.
As it stands, current NNIs address the basic infrastructure necessary to establish a call between subscriber units—mobility management, call control, and transmission control. While this is sufficient for calls made by the general public, the communications of public safety officers are typically deemed to be of priority and, therefore, the availability of the resources critical to conduct their communications should be ensured. The ability to ensure the allocation of critical resources by a second communications system is lacking in current NNIs.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.